Secretary of State Hillary Clinton said today there is "no information" the American ambassador killed in a brazen attack on a U.S. diplomatic mission in Libya was on an al Qaeda hit list.

Clinton said she had "no reason to believe that there's any basis for that," apparently referring to a report by CNN in which an unnamed source "familiar with Ambassador [Christopher] Stevens' thinking" said that the ambassador believed he was on such a list.

Stevens was killed alongside two former Navy SEALs, Glen Doherty and Tyrone Woods, and State Department computer expert Sean Smith in the Sept. 11 attack on an American diplomatic facility in Benghazi. Just weeks before his death, Doherty told ABC News he had been in Libya working with the State Department to track down thousands of dangerous surface-to-air missiles that had been looted during last year's revolution.

While top U.S. officials have changed their characterization of the attack -- from a "spontaneous, not premeditated" assault that was the result of a "hijacked" protest, as U.S. ambassador to the United Nations Susan Rice said Sunday, to an "opportunistic" "terrorist attack," as White House spokesperson Jay Carney said today -- none have said definitively who was behind it.

National Counterterrorism Director Matthew Olsen told a Senate committee Wednesday that American intelligence was "looking at indications that individuals involved in the attack may have had connections to al Qaeda or al Qaeda's affiliates -- in particular, al Qaeda in the Islamic Maghreb." At the time, Olsen said they did not have evidence the attack was pre-planned, but it was a possibility.

In a Univision town hall meeting today, President Obama declined to call the assault a terrorist attack, saying he didn't "want to speak to something until we have all the information."

A team of FBI investigators landed in Libya earlier this week, and today Clinton announced that the State Department would be launching its own separate investigation into the deadly assault.

Fox News reported early today that a former Guantanamo Bay detainee may have been involved in the attack, but U.S. officials told ABC News no individuals have been conclusively linked to the violence.

"There's an active effort to uncover those individuals and groups who were responsible for the attack," an intelligence official said. "It is safe to assume that any significant extremist in Eastern Libya is going to be under a lot of scrutiny right now."